Staff from his elementary school showed paperwork indicating that the suspect was a juvenile at the time of the December 23 attack, which would make him ineligible for the death penalty, a court source said.

A judge is expected to rule on the age in a January 28 hearing, the official said, adding that the suspect did not appear in court for the latest hearing.

The suspect says he is 17, so would face three years in a reform facility if convicted as a juvenile.

Five other men also have been charged in the case, which has put an international spotlight on sexual abuse against women in India. One of the five now says he is also under age.

Police say the 23-year-old victim and a male friend boarded the New Dehli bus on December 16 after an evening movie. But the bus turned out to be off-duty and was being driven by a group of friends who, police say, attacked the couple and then took turns raping the woman. She died two weeks later in hospital.

Deciding the young suspect's age could be complicated. He is believed to lack a birth certificate - a common occurrence in India, where many people are born at home. In such cases, school records are often used as proof of age or identity.

The principal of the suspect's former elementary school said he quit school in the third grade, about eight years ago. He declined to provide details on the school's records on the young man, but said few people from the school, in a rural, poverty-stricken part of Uttar Pradesh state, have proof of their age.

"None of these people have documents," said Shishu Pal Singh. "If the parents say he's six years old (when he is first brought to school), we list him as six years old. If he looks older, we may say he is seven."

Medical tests can indicate a person's general age, although it is unclear if the technology would be able to give a precise age.